Mucus-penetrating Particles Research Articles

In silico and in vitro assessment of an optimized QbD-guided myoinositol and metformin-loaded mucus-penetrating particle-based gel for the amelioration of PCOS.

Polycystic ovarian syndrome (PCOS) is a multi-factorial endocrine disorder affecting women of reproductive age. However, its high prevalence and the unsuccessful translation of conventional modalities have made PCOS a pharmaco-therapeutic challenge. In the present study, we explored bi-formulations (comprising metformin-loaded mucus-penetrating nanoparticles, MTF-MPPs, and myoinositol-loaded mucus-penetrating particles, MI-MPPs) incorporated in a carbomer gel tailored for intravaginal administration. For the development and optimization of the MPPs-gel, a QbD (quality by design) approach was employed, including the initial and final risk assessment, central composite design of experts, and method validation. The optimized MTF-MPPs and MI-MPPs possessed an optimum nanometric particle size (195.0 nm and 178.8 nm, respectively) and a PDI of 0.150 and 0.123, respectively, together with a negligible negative zeta potential (-5.19 mV and -6.19 mV, respectively) through the vaginal mucus. It was observed that the MPPs are small and monodisperse with a neutral surface charge. It was observed that the MPPs-gel formulations released approximately 69.86 ± 4.65% of MTF and 67.14 ± 5.74% of MI within 120 h (5 days), which was observed to be sustained unlike MFT-MI-gel with approximately 94.89 ± 4.17% of MTF and 90.91 ± 15% of MI drugs released within 12 h. The confocal microscopy study of rhodamine-loaded MPPs indicated that they possessed a high fluorescence intensity at a depth of 15 μm, while as the penetration trajectory in the vaginal tissue increased to 35 μm, their intensity was reduced, appearing to be more prominent in the blood vessels. The analyzed data of MPPs-gel suggest that the optimized MPPs-gel formulation has potential to reach the targeted area via the uterovaginal mucosa, which has a wide network of blood vessels. Subsequently, in vivo studies were conducted and the results revealed that the proposed MPPs-gel formulation could regulate the estrous cycle of the reproductive system compared to the conventional formulation. Moreover, the formulation significantly reduced the weight of the ovaries compared to the control and conventional vaginal gel. Biochemical estimation showed improved insulin and sex hormone levels. Thus, the obtained data revealed that the deep penetration and deposition of MTF and MI on the targeted area through intravaginal delivery resulted in better therapeutic effects than the conventional vaginal gel. The obtained results confirmed the amelioration of PCOS upon treatment using the prepared MPPs-gel formulation. According to the relevant evaluation studies, it was concluded that MPPs-gel was retained in the vaginal cavity for systemic effects. Also, the sustained and non-irritating therapeutic effect meets the safety aspects. This work serves as a promising strategy for intravaginal drug delivery.

KPI-121 1% for pain and inflammation in ocular surgery.

Pain and inflammation are common experiences following ocular surgery and, if uncontrolled, can compromise patients' vision, functioning and quality of life. Corticosteroid drugs are available to manage inflammation and discomfort but have limitations in penetrating the ocular mucus barrier to reach the target ocular tissues. KPI-121 1% (INVELTYS®) is a novel formulation of loteprednol etabonate that employs innovative proprietary technology to deliver nanoparticle-sized mucus-penetrating particles to the cornea. Results from clinical trials demonstrate that KPI-121 1% is effective and well tolerated. KPI-121 1% uses mucopenetrative technology for ophthalmic use and is the only US FDA-approved twice-daily ocular corticosteroid indicated for the treatment of inflammation and pain after ocular surgery.

The role of KPI-121 0.25% in the treatment of dry eye disease: penetrating the mucus barrier to treat periodic flares.

The tear film, which includes mucins that adhere to foreign particles, rapidly clears allergens and pathogens from the ocular surface, protecting the underlying tissues. However, the tear film’s ability to efficiently remove foreign particles during blinking can also pose challenges for topical drug delivery, as traditional eye drops (solutions and suspensions) are cleared from the ocular surface before the drug can penetrate into the conjunctival and corneal epithelium. In the past 15 years, there has been an increase in the development of nanoparticles with specialized coatings that have reduced affinity to mucins and are small enough in size to pass through the mucus barrier. These mucus-penetrating particles (MPPs) have been shown to efficiently penetrate the mucus barrier and reach the ocular surface tissues. Dry eye disease (DED) is a common inflammatory ocular surface disorder that often presents with periodic flares (exacerbations). However, currently approved immunomodulatory treatments for DED are intended for long-term use. Thus, there is a need for effective short-term treatments that can address intermittent flares of DED. Loteprednol etabonate, an ocular corticosteroid, was engineered to break down rapidly after administration to the ocular surface tissues and thereby reduce risks associated with other topical steroids. KPI-121 is an ophthalmic suspension that uses the MPP technology to deliver loteprednol etabonate more efficiently to the ocular tissues, achieving in animal models a 3.6-fold greater penetration of loteprednol etabonate to the cornea than traditional loteprednol etabonate ophthalmic suspensions. In clinical trials, short-term treatment with KPI-121 0.25% significantly reduced signs and symptoms of DED compared with its vehicle (placebo). Recently approved KPI-121 0.25%, with its novel drug delivery design and ease of use, has the potential to effectively treat periodic flares of DED experienced by many patients.

Oral mucus-penetrating PEGylated liposomes to improve drug absorption: Differences in the interaction mechanisms of a mucoadhesive liposome.

We investigated the feasibility of densely polyethylene glycol (PEG2000)-modified liposomes as mucus-penetrating particles (MPPs) for oral delivery of systemically absorbed peptides. The oral absorption of MPPs and mucoadhesive liposomes modified with glycol chitosan (GCS) was compared. In an in vitro artificial mucus model, the densely PEGylated liposomes showed mucus permeability. Intracellular uptake of liposomes was evaluated in a Caco-2 and mucus-secreting Caco-2/HT29 co-culture. Intracellular uptake of MPPs was unaffected by mucus in the co-culture system, whereas the cellular uptake of GCS-liposomes was lower with a mucus layer than in Caco-2 alone. Rat in vivo oral absorption of liposomes was evaluated by using fluorescein isothiocyanate dextran (FD) as a model peptide drug. Oral absorption was higher for densely PEGylated than for unmodified liposomes and was PEG-concentration dependent, but excessive PEGylation decreased FD blood concentration. PEGylated liposomes incorporating spermine (SPM) as an absorption enhancer were then designed and showed the highest in vivo absorption of FD of all tested formulations. The pharmacological effects of the oral liposomes were evaluated by using elcatonin and did not correlate with FD oral absorption. The non-PEGylated SPM liposomes showed the highest pharmacological effect, suggesting the need for drug-specific optimization of liposomal components and surface modifiers.

Mucus-Penetrating Particles and the Role of Ocular Mucus as a Barrier to Micro- and Nanosuspensions.

The ocular surface is naturally covered with a layer of mucus. Along with other functions, this mucus layer serves to trap and eliminate foreign substances, such as allergens, pathogens, and debris. In playing this pivotal role, mucus can also hinder topical delivery of therapeutics to the eye. Recent studies provide evidence that drugs formulated as traditional micro- or nanoparticles are susceptible to entrapment and rapid clearance by ocular mucus. Mucus-penetrating particles (MPPs) is a nanoparticle technology that emerged over the past decade. With a muco-inert surface and a particle size smaller than the mucus mesh size, MPPs can diffuse in ex vivo mucus essentially freely. Preclinical studies have shown that, compared with particles lacking the mucus-penetrating attributes, MPPs can improve the uniformity of drug particle distribution on mucosal surfaces and enhance drug delivery to ocular tissues.

Engineering Polymer-Binding Bispecific Antibodies for Enhanced Pretargeted Delivery of Nanoparticles to Mucus-Covered Epithelium.

Mucus represents a major barrier to sustained and targeted drug delivery to mucosal epithelium. Ideal drug carriers should not only rapidly diffuse across mucus, but also bind the epithelium. Unfortunately, ligand-conjugated particles often exhibit poor penetration across mucus. In this work, we explored a two-step "pretargeting" approach through engineering a bispecific antibody that binds both cell-surface ICAM-1 and polyethylene glycol (PEG) on the surface of nanoparticles, thereby effectively decoupling cell targeting from particle design and formulation. When tested in a mucus-coated Caco-2 culture model that mimics the physiological process of mucus clearance, pretargeting increased the amount of PEGylated particles binding to cells by around 2-fold or more compared to either non-targeted or actively targeted PEGylated particles. Pretargeting also markedly enhanced particle retention in mouse intestinal tissues. Our work underscores pretargeting as a promising strategy to improve the delivery of therapeutics to mucosal surfaces.

Preparation and performance of pH-responsive nanocarriers for mucus penetration

Objective To prepare pH-responsive osmotic nanocarriers (pMPPs), observe their distribution in the genital tract mucosa in mice, and evaluate their radiosensitizing effects in tumor cells. Methods Amphiphilic polymers containing pH-sensitive hydrazone bonds were synthesized and pMPPs were prepared by ultrasonic emulsification. At the same time, the hydrophobic polymer polylactic acid-glycolic acid copolymer (PLGA) and the amphiphilic polymer PLGA-polyethylene glycol without hydrazine bond were selected, and the mucoadhesive nanoparticles(MPs) and mucus-penetrating particles (MPPs) were prepared in the same way. Fluorescence microscopy was used to observe the distribution of three kinds of nanocarriers labeled with fluorescent dye Cy5.5 in the genital tract mucosa. The toxicity of nanocarriers to human cervical cancer cell line HeLa was tested by thiazolyl blue assay. The amphiphilic polymer containing pH-sensitive hydrazone bond was combined with oil-soluble gold nanoparticles to form a multi-encapsulated nanocarrier, and its radiotherapy sensitization effect in HeLa cells was evaluated by thiazole blue assay. Results The pMPPs were successfully prepared with relatively uniform particle size and good dispersion. Fluorescence microscopy showed that pMPPs not only had good mucus permeability, but also could improve the endocytosis efficiency of the nanocarriers in reproductive tract mucosa. The results of thiazolyl blue test showed that when the concentration of the carrier reached to 0.80 mg/ml, the survival rate of HeLa cells in the pMPPs group was higher than 90% which was higher than that in the MPs and the MPPs groups, indicating that pMPPs had good biosafety. The HeLa cell survival rate of the CMNa group (0.80 mg/ml) was higher than that of the multi-package nanocarrier group under different doses of X-ray irradiation (4 Gy: 82.90% vs. 61.79%; 8 Gy: 64.75% vs. 42.36%). This result indicated that compared with the CMNa, a commonly used clinical radiotherapy sensitizer, the multi-encapsulated nanocarriers can more effectively enhance the sensitivity of tumor cells to radiation therapy, thereby improving the lethality of radiation therapy on tumor cells. Conclusion This study solved the conflict between mucus permeation and endocytosis design of nanocarriers in mucosal tissue application, and provided new insight for the treatment of mucosal tissue diseases. Key words: pH-responsive mucus-penetrating particles; Mucoadhesive nanoparticles; Mucus-penetrating particles; Mucus; Permeability

PEGylation for enhancing nanoparticle diffusion in mucus.

The viscoelastic mucus secretions coating exposed organs such as the lung airways and the female reproductive tract can trap and quickly eliminate not only foreign pathogens and ultrafine particles but also particle-based drug delivery systems, thus limiting sustained and targeted drug delivery at mucosal surfaces. To improve particle distribution across the mucosa and enhance delivery to the underlying epithelium, many investigators have sought to develop nanoparticles capable of readily traversing mucus. The first synthetic nanoparticles shown capable of rapidly penetrating physiological mucus secretions utilized a dense coating of polyethylene glycol (PEG) covalently grafted onto the surface of preformed polymeric nanoparticles. In the decade since, PEG has become the gold standard in engineering mucus-penetrating drug carriers for sustained and targeted drug delivery to the lungs, gastrointestinal tract, eyes, and female reproductive tract. This review summarizes the history of the development of various PEG-based mucus-penetrating particles, and highlights the key physicochemical properties of PEG coatings and PEGylation strategies to achieve muco-inert PEG coatings on nanoparticle drug carriers for improved drug and gene delivery at mucosal surfaces.

PEGylated Nanoemulsions for Oral Delivery: Role of the Inner Core on the Final Fate of the Formulation.

Since the past decade, there has been growing interest to grant nanoparticles with diffusion properties across mucosae. In this sense, the nonionic block copolymer Pluronic F127 (PF127) has emerged as a promising coating agent to formulate mucus-penetrating particles. In the journey to find efficient coating agents, researchers have focused more on the effect of the coating agent architecture rather than on the role of the physicochemical properties of the nanoparticle used as the substrate. The current knowledge about mucodiffusive particles is in general based on model-like nanoparticles, such as polystyrene or poly(lactic-co-glycolic) acid nanoparticles, but there is a lack of information about the potential of PF127 on other colloidal systems. This work aims to shed some light on this issue by selecting three oils, palm (solid), coconut (semisolid), and wheat germ (liquid), with different physicochemical properties to formulate PF127-coated nanoemulsions. The obtained nanoemulsions were characterized, and their colloidal stability was tested. Their diffusion capacity was determined by particle tracking after challenging the nanoemulsions across an intestinal porcine mucus layer. In accordance with the evidence of model-like nanoparticles, our results state that PF127 allows mucodiffusion, but its effectiveness as a coating agent clearly depends on the physicochemical properties of the nanostructure core over which PF127 is placed. Among other physicochemical properties, the results certainly showed that the hydrophobic character of the nanostructure core emerges as a critical factor in the formulation of successful PF127 coatings.

Mucus-penetrating nanoparticles made with “mucoadhesive” poly(vinyl alcohol)

Nanoparticles that readily penetrate mucosal layers are desirable for a variety of biomedical applications. Nevertheless, most nanoparticles tend to be immobilized in mucus via steric and/or adhesive interactions. Contrary to the established opinion that poly(vinyl alcohol) (PVA) is mucoadhesive, we discovered that coating otherwise mucoadhesive nanoparticles with certain partially hydrolyzed PVAs can aid particle mobility in mucus. We describe two approaches to producing such mucus-penetrating particles (non-covalent modification of pre-formed nanoparticles and emulsification in the presence of PVA) and provide mobility data in human cervicovaginal mucus ex vivo as measured by multiple particle tracking and bulk permeation. When coated with PVAs that are ≥95% hydrolyzed, nanoparticles as small as ~210nm were immobilized in mucus similarly to well-established mucoadhesive controls (P>0.05). However, nanoparticles coated with PVAs that are <95% hydrolyzed penetrated mucus with velocities significantly exceeding those for the mucoadhesive controls (P<0.001) and were mobile in the bulk permeation assay.

Enhanced pulmonary delivery of fluticasone propionate in rodents by mucus-penetrating nanoparticles

Most attempts to achieve sustained drug delivery to pulmonary tissues using nanoparticles have focused on mucoadhesive particles (MAP). However, MAP become trapped in the luminal mucus layer and, as a result, are largely eliminated from the respiratory tract by mucociliary escalator and expiratory clearance, which undermines their sustained release potential. Recent studies have shown that mucus-penetrating particles (MPP) engineered to diffuse through mucus can avoid rapid mucociliary clearance in vivo and persist in the lung longer. Nonetheless, it has not been confirmed that MPP encapsulating small molecules can sustain drug release in the lung longer than MAP of similar size and core composition. As a proof of concept, we encapsulated fluticasone propionate (FP) into poly(lactide)-based MPP and MAP (both ∼200nm diameter, ∼30–35% drug loading) and evaluated their pulmonary residence by measuring FP levels in mouse lungs over 24h following intratracheal instillation. Furthermore, we evaluated the duration of action of FP MPP in a rat lung inflammation model compared to that of a non-encapsulated FP control. In rodents, pulmonary delivery of FP formulated as MPP provided a 60% higher local exposure compared to MAP and extended the single dose efficacy by at least 16h compared to non-encapsulated FP.

Impact of Surface Polyethylene Glycol (PEG) Density on Biodegradable Nanoparticle Transport in Mucus ex Vivo and Distribution in Vivo.

Achieving sustained drug delivery to mucosal surfaces is a major challenge due to the presence of the protective mucus layer that serves to trap and rapidly remove foreign particulates. Nanoparticles engineered to rapidly penetrate mucosal barriers (mucus-penetrating particles, "MPP") have shown promise for improving drug distribution, retention and efficacy at mucosal surfaces. MPP are densely coated with polyethylene glycol (PEG), which shields the nanoparticle core from adhesive interactions with mucus. However, the PEG density required to impart the "stealth" properties to nanoparticles in mucus, and thus, uniform distribution in vivo, is still unknown. We prepared biodegradable poly(lactic-co-glycolic acid) (PLGA) nanoparticles with a range of PEG surface densities by blending various ratios of a diblock copolymer of PLGA and 5 kDa poly(ethylene glycol) (PLGA-PEG5k) with PLGA. We then evaluated the impact of PEG surface density, measured using an (1)H NMR method, on mucin binding in vitro, nanoparticle transport in freshly obtained human cervicovaginal mucus (CVM) ex vivo, and nanoparticle distribution in the mouse cervicovaginal tract in vivo. We found that at least 5% PEG was required to effectively shield the nanoparticle core from interacting with mucus components in vitro and ex vivo, thus leading to enhanced nanoparticle distribution throughout the mouse vagina in vivo. We then demonstrated that biodegradable MPP could be formulated from blends of PLGA and PLGA-PEG polymers of various molecular weights, and that these MPP provide tunable drug loading and drug release rates and durations. Overall, we describe a methodology for rationally designing biodegradable, drug-loaded MPP for more uniform delivery to the vagina.

Topical Ocular Drug Delivery to the Back of the Eye by Mucus-Penetrating Particles.

Enhanced drug exposure to the ocular surface typically relies on inclusion of viscosity-enabling agents, whereas delivery to the back of the eye generally focuses on invasive means, such as intraocular injections. Using our novel mucus-penetrating particle (MPP) technology, which rapidly and uniformly coats and penetrates mucosal barriers, we evaluated if such drug formulations could increase ocular drug exposure and improve topical drug delivery. Pharmacokinetic (PK) profiling of topically administered loterprednol etabonate formulated as MPP (LE-MPP) was performed in rabbits and a larger species, the mini-pig. Pharmacodynamic evaluation was done in a rabbit model of VEGF-induced retinal vascular leakage. Cellular potency and PK profile were determined for a second compound, KAL821, a novel receptor tyrosine kinase inhibitor (RTKi). We demonstrated in animals that administration of LE-MPP increased exposure at the ocular surface and posterior compartments. Furthermore using a rabbit vascular leakage model, we demonstrated that biologically effective drug concentrations of LE were delivered to the back of the eye using the MPP technology. We also demonstrated that a novel RTKi formulated as MPPs provided drug levels to the back of the eye above its cellular inhibitory concentration. Topical dosing of MPPs of LE or KAL821 enhanced drug exposure at the front of the eye, and delivered therapeutically relevant drug concentrations to the back of the eye, in animals. These preclinical data support using MPP technology to engineer topical formulations to deliver therapeutic drug levels to the back of the eye and could provide major advancements in managing sight-threatening diseases.

Probing the interaction of nanoparticles with mucin for drug delivery applications using dynamic light scattering

Drug delivery via the eye, nose, gastrointestinal tract and lung is of great interest as they represent patient-compliant and facile methods to administer drugs. However, for a drug to reach the systemic circulation it must penetrate the “mucus barrier”. An understanding of the characteristics of the mucus barrier is therefore important in the design of mucus penetrating drug delivery vehicles e.g. nanoparticles. Here, a range of nanoparticles – silica, aluminium coated silica, poly (lactic-co-glycolic acid) (PLGA) and PEGylated PLGA – each with known but different physicochemical characteristics were examined in the presence of mucin to identify those characteristics that engender nanoparticle/mucin interactions and thus, to define “design rules” for mucus penetrating (nano)particles (MPP), at least in terms of the surface characteristics of charge and hydrophilicity. Dynamic light scattering (DLS) and rheology have been used to assess the interaction between such nanoparticles and mucin. It was found that negatively charged and hydrophilic nanoparticles do not exhibit an interaction with mucin whereas positively charged and hydrophobic nanoparticles show a strong interaction. Surface grafted poly (ethylene glycol) (PEG) chains significantly reduced this interaction. This study clearly demonstrates that the established colloid science techniques of DLS and rheology are very powerful screening tools to probe nanoparticle/mucin interactions.

Liposome-based mucus-penetrating particles (MPP) for mucosal theranostics: Demonstration of diamagnetic chemical exchange saturation transfer (diaCEST) magnetic resonance imaging (MRI)

Mucus barriers lining mucosal epithelia reduce the effectiveness of nanocarrier-based mucosal drug delivery and imaging (“theranostics”). Here, we describe liposome-based mucus-penetrating particles (MPP) capable of loading hydrophilic agents, e.g., the diaCEST MRI contrast agent barbituric acid (BA). We observed that polyethylene glycol (PEG)-coated liposomes containing ≥7mol% PEG diffused only ~10-fold slower in human cervicovaginal mucus (CVM) compared to their theoretical speeds in water. 7mol%-PEG liposomes contained sufficient BA loading for diaCEST contrast, and provided improved vaginal distribution compared to 0 and 3mol%-PEG liposomes. However, increasing PEG content to ~12mol% compromised BA loading and vaginal distribution, suggesting that PEG content must be optimized to maintain drug loading and stability. Non-invasive diaCEST MRI illustrated uniform vaginal coverage and longer retention of BA-loaded 7mol%-PEG liposomes compared to unencapsulated BA. Liposomal MPP with optimized PEG content hold promise for drug delivery and imaging at mucosal surfaces. From the Clinical EditorThis team of authors characterized liposome-based mucus-penetrating particles (MPP) capable of loading hydrophilic agents, such as barbituric acid (a diaCEST MRI contrast agent) and concluded that liposomal MPP with optimized PEG coating enables drug delivery and imaging at mucosal surfaces.

Effect of surface chemistry on nanoparticle interaction with gastrointestinal mucus and distribution in the gastrointestinal tract following oral and rectal administration in the mouse

It is believed that mucoadhesive surface properties on particles delivered to the gastrointestinal (GI) tract improve oral absorption or local targeting of various difficult-to-deliver drug classes. To test the effect of nanoparticle mucoadhesion on distribution of nanoparticles in the GI tract, we orally and rectally administered nano- and microparticles that we confirmed possessed surfaces that were either strongly mucoadhesive or non-mucoadhesive. We found that mucoadhesive particles (MAP) aggregated in mucus in the center of the GI lumen, far away from the absorptive epithelium, both in healthy mice and in a mouse model of ulcerative colitis (UC). In striking contrast, water absorption by the GI tract rapidly and uniformly transported non-mucoadhesive mucus-penetrating particles (MPP) to epithelial surfaces, including reaching the surfaces between villi in the small intestine. When using high gavage fluid volumes or injection into ligated intestinal loops, common methods for assessing oral drug and nanoparticle absorption, we found that both MAP and MPP became well-distributed throughout the intestine, indicating that the barrier properties of GI mucus were compromised. In the mouse colorectum, MPP penetrated into mucus in the deeply in-folded surfaces to evenly coat the entire epithelial surface. Moreover, in a mouse model of UC, MPP were transported preferentially into the disrupted, ulcerated tissue. Our results suggest that delivering drugs in non-mucoadhesive MPP is likely to provide enhanced particle distribution, and thus drug delivery, in the GI tract, including to ulcerated tissues.

Nanoparticle penetration of human cervicovaginal mucus: the effect of polyvinyl alcohol.

Therapeutic nanoparticles must rapidly penetrate the mucus secretions lining the surfaces of the respiratory, gastrointestinal and cervicovaginal tracts to efficiently reach the underlying tissues. Whereas most polymeric nanoparticles are highly mucoadhesive, we previously discovered that a dense layer of low MW polyethylene glycol (PEG) conferred a sufficiently hydrophilic and uncharged surface to effectively minimize mucin-nanoparticle adhesive interactions, allowing well-coated particles to rapidly diffuse through human mucus. Here, we sought to investigate the influence of surface coating by polyvinyl alcohol (PVA), a relatively hydrophilic and uncharged polymer routinely used as a surfactant to formulate drug carriers, on the transport of nanoparticles in fresh human cervicovaginal mucus. We found that PVA-coated polystyrene (PS) particles were immobilized, with speeds at least 4000-fold lower in mucus than in water, regardless of the PVA molecular weight or incubation concentration tested. Nanoparticles composed of poly(lactide-co-glycolide) (PLGA) or diblock copolymers of PEG-PLGA were similarly immobilized when coated with PVA (slowed 29,000- and 2500-fold, respectively). PVA coatings could not be adequately removed upon washing, and the residual PVA prevented sufficient coating with Pluronic F127 capable of reducing particle mucoadhesion. In contrast to PVA-coated particles, the similar sized PEG-coated formulations were slowed only ~6- to 10-fold in mucus compared to in water. Our results suggest that incorporating PVA in the particle formulation process may lead to the formation of mucoadhesive particles for many nanoparticulate systems. Thus, alternative methods for particle formulation, based on novel surfactants or changes in the formulation process, should be identified and developed in order to produce mucus-penetrating particles for mucosal applications.

Vaginal Delivery of Paclitaxel via Nanoparticles with Non‐Mucoadhesive Surfaces Suppresses Cervical Tumor Growth

Local delivery of chemotherapeutics in the cervicovaginal tract using nanoparticles may reduce adverse side effects associated with systemic chemotherapy, while improving outcomes for early-stage cervical cancer. It is hypothesized here that drug-loaded nanoparticles that rapidly penetrate cervicovaginal mucus (CVM) lining the female reproductive tract will more effectively deliver their payload to underlying diseased tissues in a uniform and sustained manner compared with nanoparticles that do not efficiently penetrate CVM. Paclitaxel-loaded nanoparticles are developed, composed entirely of polymers used in FDA-approved products, which rapidly penetrate human CVM and provide sustained drug release with minimal burst effect. A mouse model is further employed with aggressive cervical tumors established in the cervicovaginal tract to compare paclitaxel-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (conventional particles, or CP) and similar particles coated with Pluronic F127 (mucus-penetrating particles, or MPP). CP are mucoadhesive and, thus, aggregated in mucus, while MPP achieve more uniform distribution and close proximity to cervical tumors. Paclitaxel-MPP suppress tumor growth more effectively and prolong median survival of mice compared with unencapsulated paclitaxel or paclitaxel-CP. Histopathological studies demonstrate minimal toxicity to the cervicovaginal epithelia, suggesting paclitaxel-MPP may be safe for intravaginal use. These results demonstrate the in vivo advantages of polymer-based MPP for treatment of tumors localized to a mucosal surface.

Enhanced vaginal drug delivery through the use of hypotonic formulations that induce fluid uptake

Mucosal epithelia use osmotic gradients for fluid absorption and secretion. We hypothesized that administration of hypotonic solutions would induce fluid uptake that could be advantageous for rapidly delivering drugs through mucus to the vaginal epithelium. We found that hypotonic formulations markedly increased the rate at which small molecule drugs and mucoinert nanoparticles (mucus-penetrating particles, or MPP), but not conventional mucoadhesive nanoparticles (CP), reached the vaginal epithelial surface in vivo in mice. Additionally, hypotonic formulations greatly enhanced drug and MPP delivery to the entire epithelial surface, including deep into the vaginal folds (rugae) that drugs or MPP in isotonic formulations failed to reach efficiently. However, hypotonic formulations caused unencapsulated “free” drugs to be drawn through the epithelium, reducing vaginal retention. In contrast, hypotonic formulations caused MPP to accumulate rapidly and uniformly on vaginal surfaces, ideally positioned for localized sustained drug delivery. Using a mouse model of vaginal genital herpes (HSV-2) infection, we found that hypotonic delivery of free drug led to improved immediate protection, but diminished longer-term protection. In contrast, as we previously demonstrated, hypotonic delivery of drug via MPP led to better long-term retention and protection in the vagina. Importantly, we demonstrate that slightly hypotonic formulations provided rapid and uniform delivery of MPP to the entire vaginal surface, thus enabling formulations with minimal risk of epithelial toxicity. Hypotonic formulations for vaginal drug delivery via MPP may significantly improve prevention and treatment of reproductive tract diseases and disorders.

Scalable method to produce biodegradable nanoparticles that rapidly penetrate human mucus

Mucus typically traps and rapidly removes foreign particles from the airways, gastrointestinal tract, nasopharynx, female reproductive tract and the surface of the eye. Nanoparticles capable of rapid penetration through mucus can potentially avoid rapid clearance, and open significant opportunities for controlled drug delivery at mucosal surfaces. Here, we report an industrially scalable emulsification method to produce biodegradable mucus-penetrating particles (MPP). The emulsification of diblock copolymers of poly(lactic-co-glycolic acid) and polyethylene glycol (PLGA-PEG) using low molecular weight (MW) emulsifiers forms dense brush PEG coatings on nanoparticles that allow rapid nanoparticle penetration through fresh undiluted human mucus. In comparison, conventional high MW emulsifiers, such as polyvinyl alcohol (PVA), interrupts the PEG coating on nanoparticles, resulting in their immobilization in mucus owing to adhesive interactions with mucus mesh elements. PLGA-PEG nanoparticles with a wide range of PEG MW (1, 2, 5, and 10kDa), prepared by the emulsification method using low MW emulsifiers, all rapidly penetrated mucus. A range of drugs, from hydrophobic small molecules to hydrophilic large biologics, can be efficiently loaded into biodegradable MPP using the method described. This readily scalable method should facilitate the production of MPP products for mucosal drug delivery, as well as potentially longer-circulating particles following intravenous administration.